In the literature you get for it they tell you to consider 4 points of info with every scan before making a treatment decision: the current reading number, the trend arrow, the verbal message if there is one, and the graph of your day to date. So officially the trend arrow IS supposed to be useful, I just find that it only really provides reliable info at the extremes (pointing straight up or straight down is a pretty safe bet). Or if the graph shows me clearly rising or falling - but then I can just look at the graph, the arrow isn't providing me with any additional info. And for that matter the arrow and the text message usually overlap (e.g. "glucose going high" + up arrow). I think the whole thing is just built for redundancies, the end result being: "take all the data into account and use your common sense like always!"